I am so sorry for your loss and do understand how upset the certificate giving the cause of death must make you feel.
My husband passed away last summer and, after sitting through a bedside vigil lasting five days and nights, with doctors only referring to sepsis, I was taken aback when the cause of death was given as Aspiration Pneumonia - but they did at least include mention of Alzheimer's Disease too.
The clerk in the hospital bereavement office could see that I was taken aback, particularly as Aspiration Pneumonia had never been mentioned before - even when I had asked one of the doctors where the infection leading to sepsis had started, he said it was unknown and irrelevant as the sepsis was now rampant throughout his body, causing multiple organ failure.
I was told that I could talk to the consultant who had signed the certificate before I actually registered the death. I was also told that it was unlikely the consultant would change what was on the certificate, but that he might be able to explain things to me and put my mind at rest.
I spent three days trying to contact him and in the end I gave up and registered the death with the certificate I'd been given. I figured that as my husband had been having problems eating and drinking for several weeks there was probably some likelihood that the infection had started as a result of food or drink settling in the lungs at some point, even if he hadn't alerted anyone by signs of choking.
The main reason I am mentioning this is to let you know that it is possible to challenge what is written on the certificate as the cause of death before actually going to register the death. I would have been very upset if my husband's dementia had not been recorded at all.
Of course, it is such a stressful time and there is no guarantee that anything will be changed at the end of it, so it is understandable that people do not feel strong enough to put themselves through that ordeal on top of everything else they are dealing with.
I'm thinking of you.